1. Field of the Invention
The present invention relates to methods of forming carbon nanotubes, and particularly to a method of forming carbon nanotubes from carbon-rich fly ash by chemical vapor deposition.
2. Description of the Related Art
Fly ash is one of the residues generated in combustion, and is formed from the fine particles that rise with the flue gases. Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reach the chimneys of coal-fired power plants. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline) and calcium oxide (CaO), both being endemic ingredients in many coal-bearing rock strata.
Fly ash is typically seen as an environmental hazard and is considered a waste product with little to no reclamation potential. Water desalination processes, in particular, create large quantities of fly ash, typically in the form of carbon-rich flue ash. Power plants also produce large quantities of such carbon-rich fly ash, typically from crude and heavy oil processes. For example, in Saudi Arabia, water desalination plants and power plants, which are typically fueled by crude oil or heavy oil, produce large amounts of fly ash daily that may have a carbon content of 80%-90%, the remainder being oxides of silicon, aluminum, nickel, vanadium and iron. Most of this fly ash is treated as waste, and is disposed of at landfills.
Due to the environmental hazards of producing fly ash and disposal of fly ash as a common byproduct of many industrial processes, it would be desirable to provide a method for recycling the fly ash into useful components, such as reactive carbon, which could be used for other desired processes.
Thus, a method of forming carbon nanotubes from carbon-rich fly ash solving the aforementioned problems is desired.